Modern integrated circuits are formed on semiconductor chips. To increase manufacturing throughput and lower manufacturing cost, the integrated circuits are manufactured in semiconductor wafers, each containing many identical semiconductor chips. After the integrated circuits are made, semiconductor chips are sawed from the wafers and packaged before they can be used.
In a typical packaging process, semiconductor chips (also referred to as semiconductor dies) are first attached to package substrates. This includes physically securing the semiconductor chips on the package substrates, and connecting conductive pads on the semiconductor chips to conductive pads on the package substrates. Underfill material, which typically comprises epoxy, is used to secure the packages. The semiconductor chips may be bonded using either flip-chip bonding or wire bonding. The packages are then bonded to printed circuit boards (PCBs) through ball grid array (BGA) balls. Although existing packaging techniques have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.